Aether leakage is the term given to when the Aether power user is so strong and has such high amount of Aether inside his body that his skin is unable prevent it from seeping out into the air around him giving the user a sort of aura.
Power and Usage
It can be used to bost the combat abilites by the user and sometimes even as a weapon by throwing it towards the enemy.
Not much else is known as not many users that can use it has been revealed in the adventure so far.
It's however nothing that suggests that he is the only one that is able to wield it and that all the user requires is strong enough Aether powers for it to leak out from your own body to wield it.